Conventional graphics processors are exemplified by systems and methods developed to reduce aliasing using multisampling techniques that use sub-pixel samples. However, conventionally a pixel center position is used to compute fragment parameters such as color, depth, and texture map coordinates. FIG. 1 illustrates a Primitive 102 covering a portion of a Pixel 100 as is known in the prior art. A Pixel Center Position 101 is not covered by a fragment of Primitive 102, where the fragment is the portion of Primitive 102 covering Pixel 100. A Sub-pixel Sample Position 103 is within the fragment.
When one or more sub-pixel samples are covered by a fragment, but the pixel center position is not covered by the fragment, the computed fragment parameters may be inaccurate, resulting in visual artifacts in an image including the fragment. Specifically, a color discontinuity may be introduced along a primitive boundary when a pixel center position outside of the primitive is used to compute the color for a pixel. For example, the pixel may be brightened or darkened when an incorrect light map is sampled.
There is thus a need for displacing a pixel center position for a pixel such that it lies within a fragment when one or more sub-pixel samples within the pixel are covered by the fragment.